The present invention generally relates to radio frequency (RF) antennas, and particularly to a positioner or gimbal assembly for an antenna mounted to a platform subject to submarine motion such as a ship, submarine, or the like.
Millimeter-wave RF antennas intended for use aboard ships or submarines, or on similarly moving platforms face extraordinarily severe operating requirements and constraints including limited allowable swept volume, complete hemispherical coverage under significant platform dynamics, very strong/rigid gimbal structure and high radio frequency (RF) performance (e.g., effective isotropic radiated power (EIRP) and gain-to-noise-temperature-ration (G/T)). Because of the severe attenuation of practical, millimeter-wave, high-power transmission line technologies, the need for higher EIRP performance from relatively small diameter apertures has driven placement of the antenna's millimeter-wave RF power amplifier unit as close to the feed input port as possible. The size and weight of such devices, together with the desire for multi-frequency band operation, have led to a strong desire for a positioner that has the ability to accommodate relatively heavy loads on its axis. Thus, the necessity of intersecting gimbal axis driven by the need for minimum swept volume forces normal, 3-axis gimbal configurations using orthogonal axis into geometrical arrangements which significantly decrease the effective antenna aperture in order to withstand the imposed loading requirements.
Accordingly, a goal of the present invention is to provide a positioner for a compact millimeter-wave RF antenna mounted on a rapidly moving platform which provides accurate pointing of a narrow beam radio frequency (RF) radiating assembly to provide complete hemispherical coverage within a confined volume (i.e., a minimum swept volume).